Cytochromes P450 metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) which affect renal and cardiovascular functions. Current research involves: (1) characterization of CYP2J subfamily P450s at the biochemical/molecular levels; (2) studies on the regulation of CYP2J expression; (3) evaluation of the functional roles of CYP2J products in cell/organ physiology; and (4) examination of this pathway in animal models of disease (ischemic heart disease, hypertension and atherosclerosis). We have discovered a number of mammalian CYP2J subfamily members, although we have focused most of our efforts on human CYP2J2 and mouse CYP2J5. The human CYP2J2 cDNA has been cloned, expressed and characterized with respect to its tissue distribution, cellular localization and function. This enzyme is the major human P450 expressed in heart and vasculature, where it is localized to cardiac myocytes and endothelial cells, and is active in the metabolism of AA to EETs. 11,12-EET improves cardiac function following global ischemia, causes hyperpolarization of the resting membrane potential, preserves papillary muscle contraction, lengthens the time to onset of electrical uncoupling during ischemia and inhibits cardiac L-type Ca++ channel activity. 11,12-EET attenuates TNF -induced VCAM-1 expression in endothelial cells via a mechanism involving inhibition of NF- B and attenuates endothelial hypoxia-reoxygenation injury. CYP2J2 transgenic mice have been developed to study the effects of increased EETs on cardiac function in vivo. The human CYP2J2 gene has been cloned, sequenced and characterized. We have identified several CYP2J2 polymorphic variants that result in amino acid substitutions and affect catalytic efficiency. We have cloned the mouse Cyp2j5 gene, expressed the recombinant protein and shown that it catalyzes the biosynthesis of EETs. CYP2J5 is abundant in the kidney and localized to proximal tubules and collecting ducts, sites where EETs modulate salt/water transport and mediate the actions of renal hormones. Renal CYP2J5 expression is up-regulated by androgens, down-regulated by estrogens and developmentally regulated. CYP2J expression and EET biosynthesis are increased in spontaneously hypertensive rats. Cyp2j5 deficient mice have been developed to study the functional significance of this P450 in kidney development, renal physiology and blood pressure regulation.